Heart failure affects millions of people worldwide. Heart failure often manifests itself in relatively wide QRS signals, signifying a desynchronization between electrical activation of the right and left ventricles. Often, a left bundle branch block (LBBB) interrupts the normal conduction path to the left ventricle and results in the intrinsic conduction taking a relatively long time to reach the left ventricle, causing it to be activated well after the right ventricle. This abnormal conduction delay results in a very inefficient contraction, which, in turn, produces low cardiac output. With low cardiac output, patients are unable to be very active. Over time, heart failure progressively worsens as does quality of life.
While various drug therapies may help some patients with bundle branch block, electrical cardiac stimulation often proves to be more effective than drug therapy alone, especially for patients that meet certain criteria. Such electrical cardiac stimulation is referred to as cardiac resynchronization therapy (CRT), which typically involves delivering electrical stimulation to the left ventricle (e.g., for LBBB) to compensate for delay conduction of intrinsic activity to the left ventricle. With appropriate timing, CRT increases cardiac output and improves quality of life.
While CRT is often beneficial, some questions remain regarding the optimal selection criteria for prescribing CRT. For patients who meet conventional CRT implant criteria, a relatively large percentage (about 30%) of those patients do not respond to CRT therapy. Hence, a need exists for technologies to increase the likelihood that a patient will respond favorably to CRT. Various technologies discussed herein aim to meet this need and/or other needs related to cardiac condition.